Printer control relay



July 1942- J. A. SPENCER 2,291,002

PRINTER CONTROL RELAY Filed May 7, 1940 [INTER int.

llllll 'II'II I'IIII'I 'III'III ATTORNEY.

Patented July 28, 1942 PRINTER CONTROL RELAY James A. Spencer, Teaneck, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 7, 1940, Serial No. 333,714

12 Claims.

This invention relates to teleprinters.

Radio telegraph signals are subject to deformation by spurious additions to, or reductions of, the marks and spaces. When the mark is increased or decreased in length in this way, the spaces are naturally oppositely afiected. This phenomena is due to the effects of the upper atmosphere on radio transmission and the additions or reductions are likely to occur at any point in the signal pulse. When the signal is reduced in the middle portion of the pulse, it is called a split and these splits are often of sufficient time-length to produce a spurious space effect in the printer.

It is an object of my invention to eliminate alterations in the marks and spaces in signal communication by a simple relay combination of lower cost than the usual rotating distributor.

Another object is to provide an automatic arrangement for eliminating the effects of splits and a visual hand control device for compensating for the lengthening or shortening of the signal pulses.

Another object is to devise a printer or other recording relay that will be prevented from responding to spurious space lengths below a predetermined value, whereby splits do not affect the printer.

Another object is to devise a relay that can be readily controlled to increase or decrease the proportion of mark time to space time any desired amount.

Another object is to provide a visual indicator of the existing relation between the marking and spacing times of the received signals, with the provision of a regulator that permits the adjustment of this relation.

Other objects will appear in the following description, reference being had to the drawing in which:

The single figure of the drawing is a circuit diagram of a receiving system containing my invention.

Referring to the drawing, it will be assumed that the radio signals have been received in the customary way and transmitted from the receiving station to the local oflice, either as direct current pulses or tone signals, which latter are generally converted at the receiving station into direct current pulses, as in Patent 2,142,218 granted to Richard E. Mathes and myself January 3, 1939. The invention is not limited to any particular receiving and local re-transmission system, so it will be assumed that D. C. pulses of the signal appear in resistance I by an action that need not be specifically described.

Amplifier 2 has the grid 3 and cathode 4 connected respectively to the negative and positive terminals of resistor I when a signal voltage appears therein. During the time the signal pulses appear in resistor I, the negative voltage applied to the grid thereby is sufficient to block the tube. During a space or time between the signal pulses, the grid and cathode have the same potential and electron current can flow through the tube. The cathode lead of tube 2 is connected to the negative ground terminal through resistances 5 and 6.

Two amplifier tubes I and 8 have their cathodes connected together at 9 and their grids connected to different elements in the circuit to make one conduct only on signal marks and the other conduct only on signal spaces. This is accomplished by connecting the grid of tube 1 to the positive end of resistance 5 and the grid of tube 8 to the plate I0 of tube II. The cathode terminal 9 is connected to ground through the resistances I2 and I3. The grid of tube II is then connected to the positive terminal of resistance 6. A resistance I4 is connected between the positive end of resistance I2 and the plate terminal of tube II.

In referring to the positive and negative terminals of the resistances, it is not meant that these always have that polarity. It is meant that the polarity is that given when a potential drop occurs in the resistances due to current flow. When there is no drop, of course, both ends of the resistance elements have the same potential. 2

Any type of multi-element'tube may be used in the places shown on the drawing and the ones given are merely symbolic. The cathodes are shown as equipotential cathodes and the heaters are of the usual construction. These have been omitted, as heating elements are so well known that there is no need to complicate the drawing by showing them.

The principal embodiment of my invention consists of two polar relays I5, I6. One line coil I! of relay I5 is connected between the positive terminal I8 of the plate supply and the plate of tube 3. Another line coil I9 is connected between the terminal I8 and the plate of tube 1. The polarity of these coils when energized is such that when tube I conducts, the armature switch 20 is moved against space contact 2I and when tube 8 conducts it is moved against mark contact 22.

A positive terminal 23 of an appropriate source is connected to the contacts 2|, 22 through resistances 2:2, 25, respectively, and the switch tongue 26 is grounded through the negative terminal 3:8 of a suitable source and the-grounded Coil 36 is connected between the positive terminal-3:1.

negative terminal through resistance 35.

and the negative ground terminal through resistance 31, which is contiguous with resistance 35. The slider 38 is connected between ground and these two resistances so that it simultane ously decreases one while increasing the other, when manipulated by hand. Coils'33 and 36 are so connected that they are in opposition and relay It can therefore be biasedtoeither polarity ormade neutral merely by sliding contact 38 on the resistances 35; 31.

Thearmature or switch tongue 39 of relay l6 isconnected to the-positive terminal; 49 of-a supply source and the space contact'is connected to the negative ground'terminal through coil 42 ofgan indicating device 43: A compensating resistance 53' is included in this circuit. The mark contact is connectedthrough printer M and coil 45'to the ground terminal.

The indicating device 43 is essentially a double acting D. C.- ammeter and when the spaces and marks are of normal length, the pointer ifiwill take an average position, say, in the center of the dial. If the marks are lengthened, which of course decreases the spaces, the average current through coil 2 will be less, than that through-coil 45 and the needle'will swing to, say, the right. When the marks are shortened the needle willthen swing to, the left; The multipath or other atmospheric efiects that produce these errors are sufficiently uni-form over a period of time to enable an operator to counteract them by hand-adjustments. In my invention he can do this by moving the slider 38 to simultaneously and oppositely vary the magnetic strengthiof the coils 33, 35; which may shorten or lengthen, as the case may be, the space period in respect to the mark period andvice versa.

The operation is as follows:

Suppose a signal space condition exists in resistance I. This means that the grid'.3 and cathode 4 will have the same .potential and tube 2 isunblocked. Current therefore flows-through the tube and applies positive potentialstothe inputs of tubes 1 and II bythe drop in resistances 5 and 5; These tubes therefore are unblocked and conduct current.

The passage of current throughcoil l 9 inrelay l5 causes switch tongue to swing toward space contact 2!. This contact had previously been against contact 22, so that condenser 26j was charged; As soon as the contact opens between the switch tongue and mark contact 22, and be fore itengages space contact 2|, condenser 26 discharges through coils 27, 3| and 36 and, aids coil l9 inthrowing the switch. tongue against space contact 2! but holds tongue. 39 against mark contact 23". Current now flows from positive terminal 23 through'resistance 25, condenser 26, coil 21, to junction point 28,where it is met by current flowing through coils 3i] and 3| of relay I6. The resultant current then flows through opposing coil 29 to contact 2| and to ground. Coils l9 and 2'! predominate over coil 29 and the switch tongue is held against contact 2| so long as the signal space continues. The energization of coils 3i! and 3| also holds relay tongue 39 against space contact 4!, after opening the circuit at the mark contact 43". The opening of this circuit causesthe printer to respond to the signal space in the intended way.

When the signal marking pulse terminates the signal space, the negative potential in resistance l'blocks tube 2 and removes the positive drop in resistancesiand 6. At the instant that this "happens, the electron current of tube 1 is producing a negative drop in resistances l2 and 13. This dropis now suficient to substantially block tubes Tandll -or'to reduce the current to such low Values that the negative potential in resistance I4 is insufiicient to block tube 8. Tube 8, therefore; immediately conductscurrentand completely blocks tubes- 1 and H by-theincreased dropproduced-inresistances |2 and=.l31 by its electron current.

Thecurrent incoill'l and theabsence of current incoil l9 now reverses -main relay I5and throws -.1;ne switch tongue towards the mark con: tact 22; As soon as the circuit is-interrupted at contact 2 I, condenser ZS dischargeS-inth'e oppoe sitedirection throughcoils 30,- 3Land 21. This aids coil I 1- in pullingthe switch tongue against contact 22 butholds v tongue 39-against space contact 4 I As soon as contact is made at 22, current flows from-terminal 23 throughresistance 24', coil 29, to 'junction' point --2B where it divides and part flows through coil- 2"! andthe condenser 26-and the-remainderflows through coils 3 I and in and thence to ground through switch tongueifl. It will-be noted that the-current flowing-through coil 21 is in-thesame direction as the previous discharge current, so that tongue 20 is held against mark contact 22. The current in-coils 3Eland 3| is, however, reversed, so that the tongue -39- is thrown against the. mark contact 33- This causes the printer mechanism to respond toa marking signal.

The purpose of the opposing coil 291m relay I5 is to-start the relay tongue Zdinits opposite movement just i as soon as the current in... line coil IT or I9, as thecasemay be, diesdown. to a predetermined value with the decayoi. the mark signal. and. thus start. the. relay :tonguein its opposite. movement beforethe current builds up. in. the line. coil Iill. the opposite direction;

The .dischargecurrent of condenser 26rhastens the movement of tongue 26:.vvhen. it-:starts away from a contact, but the. effect. of thisjdischare current on relay. lf'is todelaythe opposite swing of the relay tongue 39, for a purpose thatwill nOW. be described;

Let :it be, supposed :that; due to atmospheric effects a split occurs in the intermediateportionpf a;marking impulse. This is a'spurious space of reduced length and relay -tongue 20 will swing to the left: intoengagement with space contactZl. However, 'relaytongue 39 will not be swung ;tO .-the-- left; asit ordinarily .wouldbe,.-because --the discharge current from condenser 26 holds. the tongue against markcontact .43.. for a sufiicienttime. to permit. the. switchtongue. 20 to.swing,.backagainst the ,markcontact 22..when thesplit ends. This. action of..the dischargecurrentof condenser 26I..can, beasuitably controlled by adjusting the resistance 32 in circuit with coils 30 and 3|. The action of the discharge current of condenser 26 does not shorten the signals. The eiTect is merely to shift them a slight amount. What is gained at the beginning is lost at the end, so the signal length does not change. The splits, however, are of such reduced length that they are affected only at the beginning.

' Let it be supposed that the effect of the upper atmosphere is such that the signal pulses are lengthened, with the resultant shortening of the signal spaces. As already stated, this is a fairly slow eiTect and the operator can note from the position of the indicator needle 46 that it occurs. He therefore can counteract it by swinging the potentiometer slide 38 to increase the action of one coil and decrease that of the other in the pair of coils 33, 36 of relay [6. By watching this needle, the operator therefore can maintain the marks and spaces of substantially normal length.

The constants of the various units may, of course, have various values, but by way of example the following values may be given for a satisfactory installation:

The dot cycles of the printer signals are 22 cycles per second. Coils l1, I9, 30 and 3| are 1.15 henrys each. Coils 21, 29, 33 and 36 are 0.277 henry each. Resistances 24 and 25 are 1,000 ohms each. Resistance 32 is 4,000 ohms. Potentiometer 35, 3'! is 1,000 ohms. The condenser 26 is l microfarad.

It will thus be seen that my improvement automatically takes care of interruptions of the signal in the center of the marking impulse and permits one, by hand-operated means, to offset the effects when produced at the ends of the marking impulse.

Obviously, the magnetic circuit of the relays need not be of the form shown in the drawing. This form has been chosen to more readily portray the action to the eye, with minimum reading of the description of the operation. This may take any form desired.

The coils and condenser need not be associated with the specific type of switch shown in the drawing. It will be apparent that the contacts 2|, 22; resistances 24, 25; the terminal 23 and the negative ground merely constitute one form of reversing switch for the coils and condenser. This reversing switch may take any desired form, such as a double pole double throw switch or any other of its equivalents.

It will be apparent that various modifications may be devised for producing the desired result and therefore the invention is not to be limited to the specific disclosure.

Having described my invention, what I claim is:

l. A polar telegraph relay system comprising a reversing switch, a coil for reversing said switch upon its energization and de-energization, a second coil for accelerating the said action of the switch, a condenser, the accelerating coil and condenser being connected in series to said switch for denser, the last-mentioned two coils and condenser being connected in series to said switch for reversal upon operation of the reversing switch, a switch and a coil for operating the last-mentioned switch connected in shunt to that part of the series circuit containing the accelerating coil and the condenser, whereby the condenser, upon the breaking of its circuit, discharges through the accelerating coil and last-mentioned coil for operating the reversing switch, upon the decay of current in the first coil, and for delaying the operation of the second-mentioned switch.

3. A polar telegraph relay system comprising a switch tongue, a pair of contacts engageable by said tongue, a line coil for operating the relay in response to incoming signals, a source of supply having one terminal connected to said contacts and the other terminal connected to said switch tongue, an accelerating coil and a condenser connected in series between said contacts, and a printer relay coil connected in shunt to the series circuit containing the accelerating coil and the condenser.

4. A polar telegraph relay system comprising a.

switch tongue, a pair of contacts engageable by said tongue, a line coil for operating the relay in response to incoming signals, a source of supply having one terminal connected to said contacts and thev other terminal connected to said switch tongue, an accelerating coil, an opposing coil, a condenser, said accelerating coil, said opposing coil and said condenser being connected in series between said contacts, and a printer relay coil connected in shunt to that part of the series circuit containing the accelerating coil and condenser.

5. A polar telegraph relay system comprising a switch tongue connected to a potential of one sign, a pair of contacts engageable by said tongue, a line coil for operating the relay in response to incoming signals, an accelerating coil, an opposing coil, a condenser, resistances connected between said contacts and a potential of another sign, sai'd assisting coil, said opposing coil and said condenser being connected in series between said contacts, and a printer relay coil connected in shunt to that part of the series circuit containing the accelerating coil and condenser.

6. A telegraph printer system comprising a printer switch, a coil for operating said switch, a coil and an adjustable resistance for biasing said switch toward opening or closing condition, means for energizing and de-energizing said coil in response to signal marks and spaces, and means to indicate the relation between the marking and spacing time periods of the message as it is received, whereby said resistance may be adjusted to counteract changes in said time periods.

7. A telegraph printer system comprising a printer switch, a coil for operating said switch, two additional coils, one aiding and one opposing the operating coil and means to vary the current in one of said additional coils for biasing said switch toward opening or closing condition, means for energizing and de-energizing the operating coil in response to signal marks and spaces, and means to indicate the relation between the marking and spacing time periods of the message as it is received, whereby said current may be varied to counteract changes in said time periods.

8. A telegraph printer system comprising a printer switch, a coil for operating said switch, two additional coils, one aiding and one opposing the operating coil and means to oppositely vary the current in said additional coils for biasing said switch toward opening or closing condition, means for energizing and de-energizing the operating coil' in response. to signal marksand spaces, and means toindicate the relation between'the marking and spacingvtime periods of the message. as it is received, whereby said current maybe. varied to counteract changes in said time periods.

9. In a printer system, a printer polarswitch, a reversing switch having. an accelerating. coil, a condenser; said condenser and accelerating coil being connected in. series and the series branch connected in shunt with the operating coil of the printer switch across the contacts of the reversingswitch.

10. In a printer system, a printer switch having an operatingcoil; a reversing switch having an accelerating coil, a condenser, said condenser and accelerating coil being connected inseries and the series branch connected in shunt with the operatingcoil of the printer. switch across a source of potential through the contacts of the reversing switch.

11.. In a printer system, a printer polarswitch, a reversing switch having stationary contacts and. a movable member adapted to engage said contacts, an accelerating coil .for the reversing switch, a condenser, said condenser and accelerating coil beingconnected in series and the series branch connected in shunt with the operating coil of the. printer switch across the contacts of the reversing switch.

12. In a printer system, a printer polar witch, a reversing switch having an operating coil, an accelerating coil and an opposing coil, a condenser, said condenser, accelerating coil and opposing coil being. connected in series across the contacts. of the reversing switch, the operating coil, of the printer switch being connected in shunt with the circuit branch containing the condenser and accelerating .coil.

JAMES A. SPENCER. 

